/* Copyright 2002-2022 CS GROUP
    * Licensed to CS GROUP (CS) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * CS licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.orekit.estimation.measurements;
  
  import java.util.Arrays;
  
  import org.hipparchus.analysis.UnivariateFunction;
  import org.hipparchus.analysis.solvers.BracketingNthOrderBrentSolver;
  import org.hipparchus.analysis.solvers.UnivariateSolver;
  import org.hipparchus.geometry.euclidean.threed.Vector3D;
  import org.hipparchus.util.FastMath;
  import org.orekit.errors.OrekitException;
  import org.orekit.estimation.Context;
  import org.orekit.frames.Frame;
  import org.orekit.frames.Transform;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.Constants;
  import org.orekit.utils.ParameterDriver;
  
  public class RangeMeasurementCreator2 extends MeasurementCreator {
  
      private final Context context;
      private final Vector3D antennaPhaseCenter;
      private final ObservableSatellite satellite;
  
      public RangeMeasurementCreator2(final Context context) {
          this(context, Vector3D.ZERO);
      }
  
      public RangeMeasurementCreator2(final Context context, final Vector3D antennaPhaseCenter) {
          this.context            = context;
          this.antennaPhaseCenter = antennaPhaseCenter;
          this.satellite          = new ObservableSatellite(0);
      }
  
      public void init(SpacecraftState s0, AbsoluteDate t, double step) {
          for (final GroundStation station : context.stations) {
              for (ParameterDriver driver : Arrays.asList(station.getClockOffsetDriver(),
                                                          station.getEastOffsetDriver(),
                                                          station.getNorthOffsetDriver(),
                                                          station.getZenithOffsetDriver(),
                                                          station.getPrimeMeridianOffsetDriver(),
                                                          station.getPrimeMeridianDriftDriver(),
                                                          station.getPolarOffsetXDriver(),
                                                          station.getPolarDriftXDriver(),
                                                          station.getPolarOffsetYDriver(),
                                                          station.getPolarDriftYDriver())) {
                  if (driver.getReferenceDate() == null) {
                      driver.setReferenceDate(s0.getDate());
                  }
              }
  
          }
      }
  
      public void handleStep(final SpacecraftState currentState) {
          try {
              for (final GroundStation station : context.stations) {
                  final AbsoluteDate     date      = currentState.getDate();
                  final Frame            inertial  = currentState.getFrame();
                  final Vector3D         position  = currentState.toTransform().getInverse().transformPosition(antennaPhaseCenter);
  
                  if (station.getBaseFrame().getElevation(position, inertial, date) > FastMath.toRadians(30.0)) {
                      final UnivariateSolver solver = new BracketingNthOrderBrentSolver(1.0e-12, 5);
  
                      final double downLinkDelay  = solver.solve(1000, new UnivariateFunction() {
                          public double value(final double x) {
                              final Transform t = station.getOffsetToInertial(inertial, date.shiftedBy(x));
                              final double d = Vector3D.distance(position, t.transformPosition(Vector3D.ZERO));
                              return d - x * Constants.SPEED_OF_LIGHT;
                          }
                      }, -1.0, 1.0);
                      final AbsoluteDate receptionDate  = currentState.getDate().shiftedBy(downLinkDelay);
                      final Vector3D stationAtReception =
                                      station.getOffsetToInertial(inertial, receptionDate).transformPosition(Vector3D.ZERO);
                      final double downLinkDistance = Vector3D.distance(position, stationAtReception);
  
                      addMeasurement(new Range(station, false, receptionDate, downLinkDistance,
                                               1.0, 10, satellite));
                  }
  
              }
          } catch (OrekitException oe) {
              throw new OrekitException(oe);
         }
     }
 
 }